In a compressor constituting an on-vehicle air conditioner, as shown in FIG. 7, a capacitor 9 is provided between a driving board 1 for driving a motor 5 and a dc power source (battery) to smooth a voltage supplied from the dc power source to the motor 5 (for example, refer to Patent Document 1).    Patent Document 1: Japanese Patent Laid-Open No. 2005-218247